Glow discharge device



Nov. 9, 1937. H, ME D 2,098,301

GLOW DI S CHARGE DEVICE Filed Oct. 5, 1935 INVENTOR By HEMENDENHALL' A TTORNEV Patented Nov. 9, 1937 UNITED STATES 2,098,301 GLOW DISCHARGEDEVICE Hallam E. Mendenhall, Summit,

to Bell Telephone Laboratories,

a corporation of New York New York, N. Y.,

N. 1., assignor Incorporated,

Application October 3, 1935, Serial N0. 43,296

8 Claims. (Cl. 250-275) This invention relates to glow discharge devicesand more particularly to such devices having a large surface coldcathode and wherein the initiation of a discharge between the cathodeand an anode is controlled by the potential upon an auxiliary or controlelectrode.

One object of this invention is to reduce the transfer current andbreakdown voltage in glow discharge devices having an auxiliary orcontrol electrode.

Another object of this invention is to obtain substantially uniform andsimultaneous activation of a large surface cathode in glow dischargedevices.

In one illustrative embodiment of this invention, a glow dischargedevice comprises an enclosing vessel having a gas, such as argon orneon,

or a mixture of gases therein, a cylindrical cathode having a coating ofthermionic material, such as barium and strontium carbonates, on one ofits surfaces, a work anode, and an ignition anode or control electrode.The work anode may be a metallic rod extending through the cathode, allbut one end portion of the rod anode being encompassed by an insulatingsleeve, and preferably extends an appreciable distance above the cathodeso that a high work gap potential may be employed.

In accordance with one feature of this invention, the auxiliary orcontrol electrode is an annular member, for example, a wire ringdisposed immediately adjacent one end of the cathode. This constructioninsures a low transfer current and hence enables control of a largedischarge between the cathode and anode by a relatively small dischargebetween the cathode and control electrode.

In accordance with another feature of this invention, the work anodesleeve is encompassed by a tubular electrode which may be electricallyconnected to the auxiliary or control electrode, and which assuressubstantially uniform and simultaneous activation of the entire coatedsurface of the cathode during the activation period.

The invention and the various features thereof will be understood moreclearly and fully from the following detailed description with referenceto the accompanying drawing, in which:

Fig. 1 is a perspective view of a glow discharge device illustrative ofone embodiment of this invention;

Fig. 2 is a perspective view of another illustrative embodiment of thisinvention wherein an auxiliary electrode is provided in cooperativerelation with the cathode for obtaining substan tially uniform andsimultaneous activation of a large portion of the cathode surface, aportion of the enclosing vessel and of the cathode being broken away toshow the auxiliary electrode more clearly;

v pair of wires or Fig. 3 is a view along line 3-3 of Fig. 2 of theelectrode structure included in the device shown in Fig. 2; and

Fig. 4 is another perspective view of still another illustrativeembodiment of this invention wherein the control electrode is an annularmember within the cathode and adjacent one end thereof, a portion of theenclosing vessel and of the cathode being broken away to show thecontrol electrode and anode more clearly.

Referring now to the drawing, the glow discharge device shown in Fig. 1comprises an enclosing vessel "I having a stem H at one end terminatingin a press l2. The vessel III has a filling of a rare gas, such as argonor neon, at a pressure of the order of 10 to 40 millimeters of mercury,or a mixture of such gases. A mixture of rare gas with mercury vapor mayalso be used. A large surface cold type cathode I3 is supported abovethe stem and may be a cylinder of nickel coated on its inner surfacewith a thermionic material, such as barium and strontium carbonates, andsupported by a wire or rod l4 embedded in thepress l2. The outer surfaceof the cylinder l3 may be treated by a calorizing process to prevent aglow discharge from occurring on the outer surface of the cylinder andto insure thereby a low potential drop between the cathode and the workanode.

Disposed immediately adjacent the upper end of and encircling thecathode i3 is an ignition anode or control electrode l5 which may be anannular band or wire of nickel supported by a rods l6 embedded in thepress l2 and which is of substantially the same diameter as the cathodel3. The control electrode l5 preferably is disposed closely adjacent theupper edge of the cathode l3 so that a discharge may be produced betweenthe cathode and control electrode by a relatively low potential and isso disposed that the transfer currents will be small. The controlelectrode l5 and cathode l3, it will be apparent, form a relativelylarge gap of uniform width so that a large portion of the cathode willbecome activated substantially simultaneously upon the application ofthe proper activation potential between the control electrode l5 and thecathode l3.

A linear rod anode 35 having bent fingers 36 at its upper end extends inthe axis of the cathode l3 and control electrode l5 and preferablyprojects an appreciable distance above the control the stem I l. A splitcylindrical cathode 20, which may be of nickel and coated on its innersurface with a thermionic material, is supported by a bent wire or rod2| embedded in the press l2. Disposed within the cathode 20 and coaxialtherewith is an anode 22, which may be a linear rod or wire embedded inthe press I2 and having a spherical end portion 23. Preferably the anode22 extends a material distance above the 1 upper end of the cathode 20so that a relatively high operating potential may be employed and alarge output obtained. All but the end portion 23 of the anode 22 isencased in an insulating sleeve 24, such, for example, as a glass tube.

An ignition anode or control electrode, which may have a coating ofthermionic material, is provided for controlling the initiation of adischarge between the cathode 20 and the spherical end 23 of the anode22, and includes a cylindrical shell 25, for example, of nickel,encompassing the sleeve 24, and coaxial and substantially coextensivewith the cathode 20, and a metallic or wire ring '26. The ring 26 isdisposed immediately adjacent the upper edge of the cathode 20 and ismechanically and electrically connected to the shell 25 by a pluralityof rigid metallic arms 21. The shell 25 and ring 26 may be supportedfrom the stem II by a pair of rods or wires 28.

The ignition anode or control electrode may bemaintained in the properspace relation with the cathode 20 by a bracing structure including aplurality of posts 29, preferably of insulating material, secured at oneend to the ring 26 and attached at the other end to a flexible disc orring 30, such as a sheet of mica, which engages the inner wall of thetubular portion I9 of the en closing vessel i8.

It will be apparent that the ring 25 and cathode 20 form a relativelylarge gap of uniform and small width so that'but a relatively smallpotential is necessary to produce a discharge between the cathode andring, and, furthermore, uniform and substantially simultaneousactivation of the portions of the cathode adjacent the ring 26 will beobtained. Moreover, the shell 25, which is at the same potential as thering 25, assures uniform activation of the entire inner surface of thecathode 20 so that a maximum current to the spherical end 23 of theanode 22 obtains very shortly after the initiation of a dischargebetween the cathode 20 and the ring 26. Although the shell 25 and ring26 have been shown and described as electrically connected, they may beelectrically separate and have suitable different potentials appliedthereto.

In still another embodiment of this invention, illustrated in Fig. 4,the ignition anode or control electrode may be an annular metallic disc3| disposed within and coaxially with the cylindrical cathode 32, coatedon its inner surface with a thermionic material, a d is positionedimmediately adjacent the lower end thereof. The disc 3| and cathode 32may be supported by rods or wires 33 and 34, respectively, embedded inthe press l2. A red anode 35 extends through the control electrode 3|and into the cathode 32, all but the upper end of the anode beingencased in an insulating sleeve H, such as a glass tube.

Although specific embodiments of this invention have been shown anddescribed, it will be understood, of course, that various modificationsmay be made therein the scope and spirit of this invention as defined inthe appended claims.

without departing from What is claimed is:

1. A glow discharge device comprising a hollow cathode having athermionic coating on one of its surfaces, an annular control electrodeimmediately adjacent one end of said cathode, a rod anode extendingentirely through said cathode and control electrode and terminatingbeyond said one end, and an insulating sleeve encompassing all of saidanode except the terminating portion thereof.

2. A glow discharge device comprising a cylindrical cathode having athermionically activated inner surface, an anode extending through saidcathode and having a portion beyond one end thereof, insulating meansencasing all of said anode but said portion thereof, and a tubularcontrol electrode within said cathode and substantially coextensivetherewith.

3. A glow discharge device comprising a hollow cathode having athermionically activated surface, an anode in cooperative relation withsaid cathode, and a control electrode including a portion adjacent oneend of said cathode and a portion extending at an angle to said firstportion and disposed in juxtaposition to said surface.

4. A glow discharge device comprising a cylindrical cathode having acoating of thermionic 1 material on one of its surfaces, an anode incooperative relation with said cathode, and a control electrodeincluding an annular member adjacent one end of said cathode and acylindrical member coaxial with said surface.

5. A glow discharge device comprising a cylindrical cathode having acoating of thermionic material on its inner surface, a rod anodeextending in the axis 01' said cathode and beyond one end of saidcathode, an insulating sleeve encompassing said anode, and a controlelectrode including a wire ring immediately adjacent said one end and atubular shell within said cathode and encompassing said insulatingsleeve.

6. A glow discharge device comprising an enclosing vessel having a stem,a tubular cathode, an electrode having an annular portion adiacent oneend of said cathode, means supporting said electrode from said stem, andother supporting means including a flexible ring connected to saidelectrode and engaging said enclosing vessel.

7. A glow discharge device comprising an enclosing vessel having a stem,a cylindrical cathode.

an electrode including an annular member adjacent one end of saidcathode and a member extending within said cathode, means supportingsaid cathode and said electrode from said stem, supporting memberscarried by said annular member, and an insulating ring carried by saidsupporting members and engaging said enclosing vessel.

8. A glow discharge device comprising an enclosing vessel having a stemand a dome opposite said stem, a cylindrical cathode above said stem, ananode in cooperative relation with said cathode, a control electrodeincluding an annular member adjacent the end of said cathode remote fromsaid stem and a tubular member within said cathode, means engaging saidtubular member for supporting said control electrode from said stem, andbracing means for said control electrode including an insulating memberconnected to said annular member and engaging the inner wall of saiddome.

